This invention relates to a brake shoe for the wheel of a railroad vehicle, both locomotive and car, and in particular to an insert engageable with the flange of the wheel to guide the friction member of the shoe acurately into contact with the tread of the wheel when the brake is applied.
Flange-guided railroad brake shoes have been in use for many years. The characteristic feature is an integral cantilevered guide projecting from one side of the backing plate of the shoe, presenting a slot to fit complementally the flange of the wheel. Because of variance in design for servicing a broad range of railroads, and because of somewhat sporadic demand, cost problems are presented by mold investment, manufacture and maintaining a variant inventory.
The primary object of the present invention is to reduce this cost by making available a flange-guided insert which can be installed at will, interposable between the brake head and the back of a standard (non-guided) shoe. More specifically, it is an object of the present invention to achieve the foregoing objective by so configuring the insert that it can be tightly retained by a standard key and at the same time secured against both longitudinal and lateral displacement.
In recent years there have been considerable changes in brake rigging for railroad vehicles, a change from hangers to unit beams for example. Another object of the invention is to employ a flange-guided insert as a guide to compensate for any loose fit due to a change in the brake rigging.
The objectives are achieved by constructing the insert to include a support plate which presents opposed shoulders for mating or keying the insert to other parts of the brake shoe assembly, thereby to prevent both longitudinal and lateral displacement of the insert. Such other parts may include the backing plate of the shoe itself, the center attaching lug of the shoe, the toe guides associated with the shoe, or a part of the brake head.
It may be desirable to have the respective surfaces which contact the wheel tread on one hand and the wheel flange on the other hand respectively perform different functions. Whereas a high friction contact between the brake shoe and wheel tread is desirable to provide a powerful brake force, a similar high friction contact between the flange guide and wheel flange may not always be satisfactory with certain types of wheels. For example, it may be desirable to provide a wheel flange contact surface of low friction material to simply perform a guiding function to maintain the brake head and shoe in their proper position relative to the wheel flange. In other instances, it may be advantageous to provide a low friction flange contact surface engageable with the wheel flange. Accordingly, it is a further object of the present invention to provide for such variant friction contact surfaces without maintaining a large inventory, as discussed above, simply by supplying inserts which may be varied or selected at will in terms of a pad or liner thereon engageable with the wheel flange, that is, a liner of whatever material is desired over the area of the flange guide which contacts the wheel flange.
A still further object of the present invention is to improve the economies of flanged shoe replacement. With more particularity, it is an object to provide a separable independent flange-guided insert which may be replaced or further utilized without regard to the amount of wear material still available on the brake shoe friction element and vice versa.